Current large size hydraulic excavating machines achieve 360 degrees of swing of the upper structure and associated work implements with a swing drive group which includes an hydraulic motor, a gear reduction mechanism, a very large swing gear, and a swing bearing. This type of swing apparatus is large and expensive and requires considerable space.
Small type of excavators, usually referred to as backhoe machines, utilize a small rotary actuator to rotate the backhoe linkage. One type of small rotary actuators is shown in U.S. Pat. No. 4,345,509, issued Aug. 24, 1982, to J. W. Gridwell et al. In this patent, a vane is bolted to the center shaft and rotates when hydraulic pressure is applied to the inner chamber. For application with a backhoe machine, the backhoe mechanism is attached to the center rotating shaft. Torque reaction is absorbed through the stator which bolts to the outer barrel of the actuator. The barrel is non-rotatable connected to the main frame, or other non-rotatable portion, of the machine. Since this type of actuator is small in diameter in order to fit between the backhoe mechanism and the frame, it has limited torque capacity and can rotate only about plus or minus 90 degrees.
The present invention is directed to overcoming one or more of the problems as set forth above.